3 files changed, 22 insertions, 48 deletions

diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index 6a47372b0b..9d166cb254 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -558,46 +558,6 @@ QPoint QHighDpiScaling::mapPositionFromNative(const QPoint &pos, const QPlatform
     return (pos - topLeft) / scaleFactor + topLeft;
 }
 
-QPointF QHighDpiScaling::mapPositionToGlobal(const QPointF &pos, const QPoint &windowGlobalPosition, const QWindow *window)
-{
-    QPointF globalPosCandidate = pos + QPointF(windowGlobalPosition);
-    if (QGuiApplicationPrivate::screen_list.size() <= 1)
-        return globalPosCandidate;
-
-    // The global position may be outside device independent screen geometry
-    // in cases where a window spans screens. Detect this case and map via
-    // native coordinates to the correct screen.
-    auto currentScreen = window->screen();
-    if (currentScreen && !currentScreen->geometry().contains(globalPosCandidate.toPoint())) {
-        QPointF nativeGlobalPos = QHighDpi::toNativePixels(globalPosCandidate, currentScreen);
-        if (auto actualPlatformScreen = currentScreen->handle()->screenForPosition(nativeGlobalPos.toPoint()))
-            return QHighDpi::fromNativePixels(nativeGlobalPos, actualPlatformScreen->screen());
-    }
-
-    return globalPosCandidate;
-}
-
-QPointF QHighDpiScaling::mapPositionFromGlobal(const QPointF &pos, const QPoint &windowGlobalPosition, const QWindow *window)
-{
-    QPointF windowPosCandidate = pos - QPointF(windowGlobalPosition);
-    if (QGuiApplicationPrivate::screen_list.size() <= 1 || window->handle() == nullptr)
-        return windowPosCandidate;
-
-    // Device independent global (screen) space may discontiguous when high-dpi scaling
-    // is active. This means that the normal subtracting of the window global position from the
-    // position-to-be-mapped may not work in cases where a window spans multiple screens.
-    // Map both positions to native global space (using the correct screens), subtract there,
-    // and then map the difference back using the scale factor for the window.
-    QScreen *posScreen = QGuiApplication::screenAt(pos.toPoint());
-    if (posScreen && posScreen != window->screen()) {
-        QPointF nativePos = QHighDpi::toNativePixels(pos, posScreen);
-        QPointF windowNativePos = window->handle()->geometry().topLeft();
-        return QHighDpi::fromNativeLocalPosition(nativePos - windowNativePos, window);
-    }
-
-    return windowPosCandidate;
-}
-
 qreal QHighDpiScaling::screenSubfactor(const QPlatformScreen *screen)
 {
     auto factor = qreal(1.0);
diff --git a/src/gui/kernel/qhighdpiscaling_p.h b/src/gui/kernel/qhighdpiscaling_p.h
index f7cf4792f2..cf21a90f70 100644
--- a/src/gui/kernel/qhighdpiscaling_p.h
+++ b/src/gui/kernel/qhighdpiscaling_p.h
@@ -123,8 +123,6 @@ public:
 
     static QPoint mapPositionFromNative(const QPoint &pos, const QPlatformScreen *platformScreen);
     static QPoint mapPositionToNative(const QPoint &pos, const QPlatformScreen *platformScreen);
-    static QPointF mapPositionToGlobal(const QPointF &pos, const QPoint &windowGlobalPosition, const QWindow *window);
-    static QPointF mapPositionFromGlobal(const QPointF &pos, const QPoint &windowGlobalPosition, const QWindow *window);
     static QDpi logicalDpi(const QScreen *screen);
 
 private:
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 131f55908b..b0c07cb632 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -2684,10 +2684,20 @@ QPointF QWindow::mapToGlobal(const QPointF &pos) const
         return QHighDpi::fromNativeLocalPosition(d->platformWindow->mapToGlobalF(QHighDpi::toNativeLocalPosition(pos, this)), this);
     }
 
-    if (QHighDpiScaling::isActive())
-        return QHighDpiScaling::mapPositionToGlobal(pos, d->globalPosition(), this);
+    if (!QHighDpiScaling::isActive())
+        return pos + d->globalPosition();
 
-    return pos + QPointF(d->globalPosition());
+    // The normal pos + windowGlobalPos calculation may give a point which is outside
+    // screen geometry for windows which span multiple screens, due to the way QHighDpiScaling
+    // creates gaps between screens in the the device indendent cooordinate system.
+    //
+    // Map the position (and the window's global position) to native coordinates, perform
+    // the addition, and then map back to device independent coordinates.
+    QPointF nativeLocalPos = QHighDpi::toNativeLocalPosition(pos, this);
+    QPointF nativeWindowGlobalPos = QHighDpi::toNativeGlobalPosition(QPointF(d->globalPosition()), this);
+    QPointF nativeGlobalPos = nativeLocalPos + nativeWindowGlobalPos;
+    QPointF deviceIndependentGlobalPos = QHighDpi::fromNativeGlobalPosition(nativeGlobalPos, this);
+    return deviceIndependentGlobalPos;
 }
 
 /*!
@@ -2716,10 +2726,16 @@ QPointF QWindow::mapFromGlobal(const QPointF &pos) const
         return QHighDpi::fromNativeLocalPosition(d->platformWindow->mapFromGlobalF(QHighDpi::toNativeLocalPosition(pos, this)), this);
     }
 
-    if (QHighDpiScaling::isActive())
-        return QHighDpiScaling::mapPositionFromGlobal(pos, d->globalPosition(), this);
+    if (!QHighDpiScaling::isActive())
+        return pos - d->globalPosition();
 
-    return pos - QPointF(d->globalPosition());
+    // Calculate local position in the native coordinate system. (See comment for the
+    // correspinding mapToGlobal() code above).
+    QPointF nativeGlobalPos = QHighDpi::toNativeGlobalPosition(pos, this);
+    QPointF nativeWindowGlobalPos = QHighDpi::toNativeGlobalPosition(QPointF(d->globalPosition()), this);
+    QPointF nativeLocalPos = nativeGlobalPos - nativeWindowGlobalPos;
+    QPointF deviceIndependentLocalPos = QHighDpi::fromNativeLocalPosition(nativeLocalPos, this);
+    return deviceIndependentLocalPos;
 }
 
 /*!